Well, that $3000 of imputed income for full time students is baked into the law.
But I really think you need to reconsider your thinking here.
By excluding $3000 of care costs, you probably saved around $900 in federal and state income tax, depending on the state you live in. So your net cost of care was not $11,000, but $10,100. Its true that if your spouse had worked instead of gone to school, you could have excluded another $2000 of the care costs, saving another $600 in income taxes. But your spouse would not then have had the benefit of the education, which you must have thought was worth something. And, if she had simply stayed home and cared for the child, you would have saved the entire $10,100 in net child care costs, but again, foregoing the education that presumably has some benefit. Making major lifestyle choices based on $600 of tax savings doesn't make a lot of sense to me.
And incidentally, if she had even a small part time job and earned over $5000, you could have excluded the entire $5000 FSA limit from taxation. You may want to think about that if you are in the same situation this year (expensive care, full time student, $5000 FSA).
